The unidentified gunman is said to have opened fire at the Borderline Bar & Grill in Thousand Oaks, which is part of the Greater Los Angeles area in California.
Dozens of terrified people hid under the tables during the shooting.
It is believed the gunman is still at large and at least one police officer is reported to be injured and is being treated at the scene.
When officers first responded they reported there was additional gunfire and said approximately 30 had been fired.
Officers believe victims will be at mulitple scenes as they fled.
At least four ambulances were called to the scene to treat multiple victims, according to the Ventura County Star.
The Ventura County Deputies responded to reports gunman firing a semi-automatic gun at 11:20pm local time.
Dozens of officers were called to the scene.
Ventura County Sheriff’s Office Capt. Garo Kuredjian said: “It’s still a very active scene.”
The suspect was originally reported to be in the bar when police arrived.
Officers found a man on the ground at the scene outside a window at the bar, but it is unclear if he is the shooter or a victim or if he had been wounded.
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